Fuel Injectors typically utilize one or more electronically controlled valves to control fuel injection quantity and timing independent of engine crank angle. In some instances, the electronically controlled valve takes on a typical structure that utilizes a relatively hard non-magnetic valve member that is attached by some means to a relatively soft magnetic armature. When a solenoid coil is energized, the armature is drawn toward the coil, and the valve member is moved toward or away from a valve seat. Because of many factors including the high number of impact cycles, the presence of liquid around the armature, acceleration from the coil and inertia factors, making a robust attachment strategy between the armature and the valve member to survive this hostile environment over many millions of actuation cycles, and do so at a reasonable cost, can be somewhat problematic.
Besides the repeated accelerations and decelerations encountered by these electronically controlled valves, other problems have been associated with consistently manufacturing large quantities of valves with relatively small air gaps that allow for relatively short valve travel distances. Those skilled in the art recognize that short travel distances are often desirable since they correlate closely to quick valve response times. Thus, insuring good perpendicularity between the armature and the valve member can allow for tighter tolerances and reduced air gap distances, and a corresponding decrease in valve response time.
In one previous valve assembly structure that addressed these problems, the valve member included an annular shoulder upon which a spacer would be supported. An armature having a guide clearance with the valve member sits atop the spacer with a relatively tight guide clearance. The perpendicular plane of the shoulder and the tight guide clearance supposedly insure good perpendicularity. Atop the armature is another spacer followed by a threaded nut that would hold the two spacers and armature securely against the shoulder of the valve member. While such a solution provides adequate long term robustness to withstand the repeated accelerations and decelerations, relying upon interactions between supposedly perpendicular surfaces on the components themselves to insure perpendicular geometry, especially at edges of the armature remote from the valve member centerline can be more problematic.
Another potential solution, which is taught in co-owned U.S. patent application Ser. No. 11/073,571, filed Mar. 8, 2005, teaches the idea of using an orientation neutral interface between the armature and the valve member, utilizing a fixture to arrange the pieces with good perpendicularity, and then welding the armature directly to the valve member. While such a strategy probably improves upon the perpendicularity issues of the previously discussed strategy, the welded joint between the armature and the valve member may not be as robust as the usage of a nut and spacers. An orientation neutral interface might be one in which the valve member includes an annular raised rounded portion upon which the armature can be press fit in a variety of orientations (plus or minus a fraction of a degree) to allow for setting in a fixture to achieve relatively near perfect perpendicularity. This alternative also has the undesirable feature of having to leave a portion of the valve member less heat treat hardened in order to make it “weldable.” While this strategy has shown promise, a valve member with a relatively small diameter reduces the amount of weld interface available, which may not provide as robust an attachment as other strategies.
The present disclosure is directed toward one or more of the problems set forth above.